1. Field of the Invention
The present invention relates to a vehicle license plate recognition method and a system thereof, particularly to a method, which can tolerate images captured from various viewing angles in any environment, and which can efficiently eliminate noise from images and fast define the region where the vehicle license plate exists to be recognized in real time.
2. Description of the Related Art
In the field of image processing, the vehicle license plate recognition technology has contributed much to public security and cost reduction via applying to automatic tolling, parking lot management, stolen vehicle detection, etc.
In applications of the vehicle license plate recognition technology, scenes including complicated contents like advertisement signs and traffic signs will disturb the accuracy of recognition; noisy backgrounds of the license plate, the color and style of the vehicle license plate, the decorative accessories, etc., may also affect the result of recognition; various illumination environments, such as daytime, night, rainy day, etc., will also lead to the failure of recognition; different viewing angles will capture inclined license plates. All the abovementioned factors would increase the difficulty of recognizing a vehicle license plate. Further, lights, bumpers, logos, frames, screws and characters on vehicles may have some similar features to those of vehicle license plates and thus will disturb the accuracy of license palate recognition. In conventional license plate recognition technologies, the vehicle license plate will be first binarized to two levels (black and white). Next, the output of binarization is partitioned into several pieces of character-related data through histogram projection. Next, the several pieces of character-related data are input into a classifier, which has been trained for recognizing characters. Then, the recognition results are assembled to obtain a complete license plate identifier (for recognizing characters on the vehicle license plate). The conventional recognition methods are likely to be influenced by noise or contamination on the vehicle license plate. In an image of a vehicle, the license plate often occupies only a small area. However, the small area contains not only the characters of the license plate but also the surroundings of characters. In such a case, it is less likely to obtain stable binarized data. Consequently, a satisfactory recognition result is hard to obtain from the binarized information containing a great amount of noise.
Therefore, the topic subject of the vehicle license plate recognition system is to improve the recognition ability and computation speed thereof. Accordingly, the present invention proposes a vehicle license plate recognition method and a system thereof to overcome the abovementioned problems.